Darrin Spivey, and his 15-year-old son Dillon Sanchez (inset) were found dead in an underwater cave.Tampa Bay Times/Zumapress.com and Facebook/WTSP (inset)

ST. PETERSBURG, Fla. — A father and son who went diving on Christmas Day with new equipment the boy got for a present have been found dead in an underwater cave at a north Florida wildlife refuge.

The Hernando County Sheriff’s Office said Thursday that Holly King called authorities after her fiancé, Darrin Spivey, and his 15-year-old son Dillon Sanchez didn’t return home after a planned dive in the 300-foot deep Eagle Nest Sink cave about an hour and a half north of Tampa.

A sign near the entrance to the cave reads: “Cave diving in this area is extremely dangerous — even life threatening!! Do not dive unless you are a certified cave diver!!”

According to the sheriff’s office, the 35-year-old Spivey was a certified diver; however, he was not a certified cave diver. They say Sanchez was not a certified diver.